1. Field of the Invention
The present invention relates to a process for producing optically active 4-hydroxy-2-cyclopentenone, to a precursor thereof and to a process for producing the precursor.
2. Description of the Related Art
Optically active 4-hydroxy-2-cyclopentenone is a compound useful as an intermediate for prostaglandins, anticholesterol agents, and the like. Known process for producing the compound include (1) one which comprises converting 4-hydroxy-2-cyclopentenone into its ester and hydrolyzing the ester with the aid of an enzyme (Japanese Patent Kokai (Laid-open) No. 63-000292), (2) one which comprises converting 4-hydroxy-2-cyclopentenone into its ester, reacting the ester with an optically active 1,6-diphenyl-4,4-hexadiyne-1,6-diol derivative to form a complex, separating the complex, then subjecting the complex to ligand exchange to obtain an ester of optically active 4-hydroxy-2-cyclopentenone and hydrolyzing the ester obtained (Japanese Patent Kokai (Laid-open) No. 63-179848) and (3) one which comprises reacting 4-hydroxy-2-cyclopentenone with an optically active lactone to obtain an ether compound, separating the ether compound into isomers and hydrolyzing the intended isomer (Japanese Patent Kokai (Laid-open) Nos. 57-159777, 60-199848 and 61-236742).
These processes, however, all have shortcomings in that it is indispensable for the processes once to convert 4-hydroxy-2-cyclopentenone into its derivative by esterification, etherification or such, and further they involve complicated separating operations, so that they are not satisfactory from the industrial viewpoint.
Recently, an attempt has been made to obtain from 4-hydroxy-2-cyclopentenone a corresponding optically active compound without protecting the hydroxyl group of the former (Japanese Patent Kokai (Laid-open) No. 4-66550). However, the results thus far obtained are not yet satisfactory.
In view of the situations, the present inventors have made extensive study on the process for producing optically active 4-hydroxy-2-cyclopentenone. As the result, it has been found that an optically active complex consisting essentially of optically active 4-hydroxy-2-cyclopentenone and an optically active propargyl alcohol derivative can be obtained in the form of crystal when racemic 4-hydroxy-2-cyclopentenone is reacted with the optically active propargyl alcohol derivative and further that optically active 4-hydroxy-2-cyclopentenone can be produced in a high optical yield and with an industrial advantage by decomposing the optically active complex obtained above without requiring to convert the racemic 4-hydroxy-2-cyclopentenone into its derivatives. The present invention has been accomplished on the basis of the above finding.